So I see these messages on my boyfriend's phone.. let's not talk about how I saw them, please. So they started off being from his bday last year when a girl says happy bday.. so he was out for a stroll and sent her a bunch of photos (the same ones he sent to me that same day). A few months later there's a message from her asking when he is going to come visit her, now he sometimes works where she works so I don't know if that's work relates or what (he replies I'll be there wed and fri). Then a week later she messages asking are you coming to say goodbye, I don't know where she was going btw (he replies saying, I'm not sure you can handle anymore goodbyes). Then just recently there is a message asking him to do a job (work) for her, he teases saying why did you leave it so late to ask me, then says I suppose I can let you off this one time. Then most recent there's a message from him to her saying "the perfume on the cash was a nice touch 😋" ( he did a job for her), she replies saying it was because it had been in her bag and then told him not to flatter himself. I know they will be working together again for who knows how long for. She sounds very flirty but he is not repelling her and is also now flirting back with her. Thing is she's like 18 and he's 32. But the worst thing is we have had so many discussions and arguments about how I find flirting while in a relationship completely unacceptable, yet he goes and does this. Thoughts?